The Essential Guide
to Huck BOM and Avdel Avbolt

When a bolt is inserted into a pre-drilled hole, the blind bolt installation tool creates pressure on the collar to form a solid connection as the expander collapses the pin on the blind side to form a finished and permanently clamped assembly. Installation is fast and easy, and more importantly, it is easy to inspect to ensure the installation has been done properly.

There are various characteristics to consider when choosing the right blind bolt. You need to choose the right grip range length and diameter for optimal strength and lasting performance. You usually can find the right blind bolt dimensions by consulting the manufacturer’s range chart. You also have to choose the right material. Most commercial blind bolts are made of steel, but there are alternate materials, such as stainless steel and titanium blind bolts, for specialty applications such as aerospace. Once you select the right blind bolt for the job, you will have an extremely strong and lasting joint.

To ensure optimal installed length and integrity of the fastened joint, you need to choose the proper length (i.e., grip range) of the fastener. The fastener grip range and corresponding overall length is obtained from the manufacturer’s data sheet. The grip range required equals the total thickness of the material to be fastened. Special grip gauges inserted into the pre-drilled hole can be used to determine the right bolt size for the strongest join. Unfortunately, there is no universal standard for blind bolt grip lengths, so each vendor has its own grip gauge.

In addition to being strong, blind bolts are resistant to vibration. Once installed, they will not work loose over time or weaken under constant shaking. That is why they have become the fastener of choice for airplanes, railway cars, automobiles, factory equipment, mining equipment, ships—any application in which the bond has to maintain a strong connection under ongoing vibration.

Another attractive feature is that blind bolts are tamper-proof. Because they are installed using special equipment and have no screw heads, they can’t be vandalized, making them ideal for use in public transit systems, public restrooms, public buildings, or anywhere vandalism is an issue. The core bolt itself is very hard, which makes it difficult to remove without special equipment from the manufacturer. If you have the right equipment, you can remove a blind bolt and leave the parent material and the pre-drilled hole undamaged.

Wooden planes could no longer meet the needs of aircraft design, so engineers started to design airplanes made of aluminum, a material that was stronger, yet light enough for aircraft design. Initially, these aluminum airplanes were made using solid rivets, which made assembly slow and required two workmen, one on each side of the material being assembled. To address the problem, Jacques Chobert, one of the engineers at Aviation Developments, created a new riveting technology, the Chobert® riveting system, which could be installed from one side by one worker. Installation was still slow because fasteners had to be loaded and installed one at a time, so Aviation Developments created a tool that could hold multiple fasteners, which considerably sped up production.

This was the birth of the blind fastener. Using a handheld tool, one worker could join materials from one side, substantially reducing assembly time and costs. The Chobert fastener was quickly adopted for British aviation manufacturing and, among other applications, was used to assemble the 20,000 Spitfire aircraft that were used in the Battle of Britain.

Since World War II, the blind bolt has evolved to become a mainstay of manufacturing. New materials were adapted, as were new head configurations and designs. New methods were developed to machine the blind bolts so they became virtually invisible when painted. With these improvements, blind bolts became common in making aircraft ailerons and flaps, doors, floors, elevators, and so on. Pneumatic tools also were developed to speed up assembly.

Over time, blind bolts were being made to join thin-gauge steel, plastics, fiberglass, and other materials. The automotive and electronics industries standardized blind fasteners for assembly uses. As new applications in aerospace and transportation emerged, new blind bolts were developed, capable of handling more extreme loads and temperatures. Uniquely designed structural rivets such as the Avdel Monobolt, Huck Magnalok, and Huck Magnabulb were developed for thin sheet materials. Eventually, blind bolts came to be used in place of rivets or bolts because of their ease of installation and superior performance.

Today, we have a wide range of blind bolts and blind bolt tools suitable for any manufacturing setting, workshop, or field repair application.

In addition to aviation, for example, they are used in railroad car assembly because of their strength and resistance to vibration. They are commonly used in shipbuilding because they create a lasting bond, and when they are made from materials such as composites or brass, they resist corrosion. They also are used in electronics manufacturing to connect circuit boards and to create tamper-proof housings.

Blind bolts are commonly used for manufacturing heavy equipment and repairing trucks and trailers. For example, Arconic Fastening Systems has the Huck BOM® (Blind, Oversized, Mechanically locked) blind bolt, as well as an entire line of Huck fasteners for trucks and trailers. The advantage of using blind bolts and lock bolts is that they are easy to install and require no maintenance; once they are installed, they don’t require checking or occasional tightening, unlike regular bolts.

Huck also offers truck repair kits that include pneumatic or hydraulic installation tools that can accommodate specialty blind bolts such as the BOM, as well as kits that can install lockbolt systems such as the Huck-Spin, Huck-Spin 2, and Bobtail HuckBolts or other types of Huck fasteners for a permanent repair.

Huck’s BOM is specifically designed to provide high clamp and tensile strength in high-vibration applications. These blind bolts offer an alternative to welding and produce a tighter join with a large blind-side footprint. The Huck BOM has a very high tensile strength and is tough enough for heavy-duty applications such as rail cars and military equipment. Installation is so easy that it takes the average worker less than 10 minutes, and using a BOM eliminates the need for welders or specially trained workers. In fact, the BOM can be used for all blind side joints and there is no risk of human error. You can even install Huck BOM fasteners using existing tools.

Avdel’s Avbolt also is designed for heavy-duty application such as shipbuilding, automotive assembly, making mining equipment, and construction. It has a high tensile strength and is tamper-resistant, and features a mechanical lock that creates a joint that resists vibration. It’s also easy to install with little or no training, and can be inspected quickly to ensure it is properly installed.

For example, the heads and collars are designed to provide added strength when used with materials of different densities or thicknesses, e.g., fiberglass or thin sheet metal.

To create a secure fit, the blind bolt collar is inserted into a pre-drilled hole. When the installation tool is triggered to pull on the pintail, a bulb is formed on the blind side. The force of pulling the pin draws the separate pieces together. The collar is then swaged to secure it to the pin and form a tight connection. Swaging also increases resistance to vibration.

Once the pin is swaged, the tool ejects the fastener pintail, also known as the stem. When installation is done properly, the pin should be nearly flush with the collar. Ideally, the pin separation should be clean as well as flush to avoid the need for additional grinding.

For optimal strength, blind bolts also are available in different sizes and grip lengths. The most common sizes are 3/16 inches, 1/4 inches, 5/16 inches and 3/8 inches, although there are larger sizes available for applications that require a stronger bond and greater shear strength.

Pneumatic – Pneumatic tools are best for use in a factory setting, in the repair shop, or where trailing hoses are less of a concern. Powered by air pressure, pneumatic tools make for fast installation and are easy to operate. Arconic has a variety of pneumatic guns to accommodate blind bolts, including the Model 254 and Model 256, which can accommodate blind bolts from 3/16 inches to 3/8 inches. Avdel has a line of pneumatic installation tools as well, including the new XT family of installation tools.

Hydraulic – In addition to pneumatic tools, manufacturers offer hydraulic tools that also are well-suited for factory or shop applications. Huck offers hydraulic installation tools as well, such as the Powerig® Hydraulic Power System, which uses a hydraulic fluid reservoir under pressure. The Powerig is available in a variety of models to accommodate bolts of any size and any application, including heavy-duty installations.

Avdel offers a full line of hydraulic installation tools powered by lightway Enerpac hydraulic power units. The 73200 tool is meant for heavy-duty use over long periods of time and can be fitted with different nose assemblies based on the bolt size. The AV™ Series of hydro-electric power tools is ergonomically designed for operator comfort and is durable in extreme conditions. It is also flexible, with the ability to set Avbolt sizes from 3/16 to 5/8 inches.

Battery-operated – Although you can use hydraulic and pneumatic installation tools in the field with a power source such as a generator, using hose-powered tools on a job site can be cumbersome and dangerous. More portable, battery-operated tools, such as the Huck Range Force BV4500 and the Avdel POP Proset cordless riveter, are available for on-the-job installations.

Avdel Avbolt – Specifically designed for heavy-duty fastening applications, the Avdel Avbolt is suitable for applications such as buildings, railway cars, containers, mining equipment, and bridges. The Avbolt is designed to be high-strength and tamper-resistant, and when it is installed at minimum grip, the stem shears above the collar and has a larger footprint on the blind side for maximum strength.

The Avbolt also features an extremely high tensile strength and shear strength, which is usually only associated with lockbolts, with the added benefits of blind installation, including in areas where access is restricted. Like all blind bolts, Avbolts are simple to install and require minimal operator training. The finished join is vibration-resistant and will not loosen over time.

The Avbolt also comes in a range of sizes from 3/16 inches to 5/8 inches (4.8 mm to 16mm). The stem is made of alloy steel and black oxide, and the sleeve and collar are made of carbon steel that is zinc-plated with a clear passivated finish. Flanged collars also are available in 3/8-, 1/2-, and 5/8-inch diameters as three-piece bolts.

Huck BOM – Arconic’s Huck BOM blind bolts are extremely tough and vibration-resistant, so they are used in military equipment, auto suspensions, amusement park rides, and other applications that require a strong, lasting join. These blind fasteners are ideal for high-tensile applications and are easy to install using any standard riveting tool.

BOM fasteners are available in sizes ranging from 3/16 inches to 3/4 inches and are made with a low-carbon steel sleeve, a medium-carbon steel pin, and a zinc-plated clear chromate finish.

The Huck BOM also features a mechanical lock that creates a vibration-resistant join and eliminates loose stems. When correctly installed, the pin will separate flush with the collar so no additional grinding is required. The collar is locked to the pin via a swaging process, and large bearing areas are created on both sides of the join.

These are just two of the most popular blind fasteners. Bay Supply offers a wide range of fasteners for multiple applications, and our experts can assist you in finding the right blind bolt for any job.